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Experimental and Numerical Evaluation of Lightning-Induced Degradation of Fastened Composite Systems

LOUISA MICHAEL, DEREK R. TUCK, PHILIPP A. BOETTCHER, BRIAN P. JUSTUSSON, BRIAN A. CARPENTER

Abstract


Aerospace composite laminate construction is widely used in various airframe components. Composite structures are often joined with other structure and substructure via fasteners that are inevitably exposed to lightning strike currents. The interaction of a lightning strike with a fastener can lead, through complex electrical, mechanical, and thermochemical processes, to the degradation of the strength of the fastened structure. Although degradation can often be seen on the surface as damage via paint discoloration, surface ablation, or surface delamination, a larger subsurface volume of material might be affected by the electrical current and thermo-chemical processes resulting in a heat affected zone and multi-planar delamination. Together, these effects have the potential to degrade the structural performance of the joint. In this work, a series of electro-mechanical tests is performed in order to evaluate the effect of lightning strikes of varying amplitudes on structural composite. The experimental methodology includes subjecting a single-fastener aerospace-composite lap joint to scaled Awaveform electric current pulses to determine the combined electromagnetic and structural effect on the system. Following the electrical test, the tested articles undergo a non-destructive inspection to quantify the extent of the damage, from which the relation between heat-affected zones extents and current levels is given. Finally, electrically-tested articles undergo a bearing test and the structural effect of the lightning strike on the structural properties of the fastened system is determined and implications on composite structural performance is assessed.


DOI
10.12783/asc37/36377

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